This invention relates to an improved compound gripper means of the type used, for example, on remote manipulators and robotic devices. The gripper comprises a way to assure release of a smooth article from a high-friction gripping surface which surface also tends, too often, to adhere to the article being gripped.
In recent years, a considerable amount of work has gone into laboratory robots. Systems have been developed for robotic methods for carrying out automatic pipetting, filtering, dilutions, spectometry, titrations of various sorts, and other automatic procedures involving organic synthesis, testing, and sample preparation. Much of the robot-automated work is preparative in nature and more of it is in the nature of providing analytical systems for use in a wide variety of applications such as analysis of polymers, food samples, extraction of drugs from biological fluids and so on. A large number of such procedures are described in Advances in Laboratory Automation Robotics (Zymark Corporation, Hopkinton, Mass., 1985).
As the work in laboratory robotics proceeded, various devices were developed which put increased demands on the fundamental equipment normally associated with robotic manipulation. For example, a lab bottle capper is described in U.S. Pat. No. 4,607,196 to Abrahams and Carll which required that a gripper of lab containers hold the container sufficiently tight to accommodate the unscrewing of container caps. Another change which took place, as the implementation of robotics-automated processes became more widespread, was the increasing unpredictability of the exact container that might be used with a given gripper. This made it impossible to determine the gripping pressure which would be used by a particular apparatus.
One result of these changes was that there was a small, but unacceptable, number of incidents where a container stuck to the surface of a gripper when it was to be released. Such grippers were often surfaced with polyurethane gripper pads, usually cast in place and having the desirable high-static-friction gripping properties required for secure holding of vials, test tubes, and bottles, etc.
Such tube-sticking problems usually manifested themselves when these somewhat organic resilient organic resin pads were used on the grippers. The inherent properties of some otherwise-desirable resinous pad materials promoted the undesirable sticking action. However, particularly in the laboratory environment, exposure to the environment can also promote the formation of sticky surfaces on pads.
The present inventor addressed himself to providing a gripper that would be free of such sticking problems but would maintain its gripping efficiency.